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FreeBSD-SA-21:12.libradius                                  Security Advisory
                                                          The FreeBSD Project

Topic:          Missing message validation in libradius(3)

Category:       core
Module:         libradius
Announced:      2021-05-26
Credits:        leommxj and Swings from Chaitin Security Research Lab
Affects:        All supported versions of FreeBSD.
Corrected:      2021-05-26 19:45:31 UTC (stable/13, 13.0-STABLE)
                2021-05-26 20:36:29 UTC (releng/13.0, 13.0-RELEASE-p1)
                2021-05-26 20:39:35 UTC (stable/12, 12.2-STABLE)
                2021-05-26 20:40:23 UTC (releng/12.2, 12.2-RELEASE-p7)
                2021-05-26 20:41:31 UTC (stable/11, 11.4-STABLE)
                2021-05-26 20:41:58 UTC (releng/11.4, 11.4-RELEASE-p10)
CVE Name:       CVE-2021-29629

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:https://security.FreeBSD.org/>.

I.   Background

libradius(3) is a client and server library implementing the Remote
Authentication Dial In User Service (RADIUS) protocol.  It is used by
pam_radius(8) and mpd5 (available in the ports tree as net/mpd5).

II.  Problem Description

libradius did not perform sufficient validation of received messages.

rad_get_attr(3) did not verify that the attribute length is valid before
subtracting the length of the Type and Length fields.  As a result, it
could return success while also providing a bogus length of SIZE_T_MAX -
2 for the Value field.

When processing attributes to find an optional authenticator,
is_valid_response() failed to verify that each attribute length is
non-zero and could thus enter an infinite loop.

III. Impact

A server may use libradius(3) to process messages from RADIUS clients.
In this case, a malicious client could trigger a denial-of-service in
the server.  A client using libradius(3) to process messages from a
server is susceptible to the same problem.

The impact of the rad_get_attr(3) bug depends on how the returned length
is validated and used by the consumer.  It is possible that libradius(3)
applications will crash or enter an infinite loop when calling
rad_get_attr(3) on untrusted RADIUS messages.

IV.  Workaround

No workaround is available.  Systems not making use of libradius(3) are
unaffected.

V.   Solution

Upgrade your vulnerable system to a supported FreeBSD stable or
release / security branch (releng) dated after the correction date.

Perform one of the following:

1) To update your vulnerable system via a binary patch:

Systems running a RELEASE version of FreeBSD on the amd64, i386, or
(on FreeBSD 13 and later) arm64 platforms can be updated via the
freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

2) To update your vulnerable system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

[FreeBSD 13.0, 12.2]
# fetch https://security.FreeBSD.org/patches/SA-21:12/libradius.patch
# fetch https://security.FreeBSD.org/patches/SA-21:12/libradius.patch.asc
# gpg --verify libradius.patch.asc

[FreeBSD 11.4]
# fetch https://security.FreeBSD.org/patches/SA-21:12/libradius.11.patch
# fetch https://security.FreeBSD.org/patches/SA-21:12/libradius.11.patch.asc
# gpg --verify libradius.11.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile the operating system using buildworld and installworld as
described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>.

Restart all daemons that use the library, or reboot the system.

VI.  Correction details

This issue is corrected by the corresponding Git commit hash or Subversion
revision number in the following stable and release branches:

Branch/path                             Hash                     Revision
- -------------------------------------------------------------------------
stable/13/                              bec0d2c9c841    stable/13-n245765
releng/13.0/                            7d900abe6269  releng/13.0-n244743
stable/12/                                                        r369859
releng/12.2/                                                      r369864
stable/11/                                                        r369866
releng/11.4/                                                      r369867
- -------------------------------------------------------------------------

For FreeBSD 13 and later:

Run the following command to see which files were modified by a
particular commit:

# git show --stat <commit hash>

Or visit the following URL, replacing NNNNNN with the hash:

<URL:https://cgit.freebsd.org/src/commit/?id=NNNNNN>

To determine the commit count in a working tree (for comparison against
nNNNNNN in the table above), run:

# git rev-list --count --first-parent HEAD

For FreeBSD 12 and earlier:

Run the following command to see which files were modified by a particular
revision, replacing NNNNNN with the revision number:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29629>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-21:12.libradius.asc>
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